Magnetic flowmeters (or mag meters) measure flow by Faraday induction, an electromagnetic effect. The magnetic flowmeter energizes a coil which generates a magnetic field across a section of a flow body assembly. The magnetic field induces an electromotive force (EMF) across the flow of conductive process fluid. The resulting potential developed across the conductive fluid is measured using a pair of electrodes that extends into the flowing process fluid. Alternatively, some magnetic flowmeters employ capacitive coupling between the electrodes and the process fluid such that the EMF can be measured without direct contact. In any event, the flow velocity is generally proportional to the induced EMF, and the volumetric flow is proportional to the flow velocity and the cross-sectional area of the flow body.
Magnetic flowmeters are useful in a variety of fluid flow measurement environments. In particular, the flow of water-based fluids, ionic solutions and other conducting fluids can all be measured using magnetic flowmeters. Thus, magnetic flowmeters can be found in water treatment facilities, beverage and hygienic food production, chemical processing, high purity pharmaceutical manufacturing, as well as hazardous and corrosive fluid processing facilities. Magnetic flowmeters are also often employed in the hydrocarbon fuel industry.
Magnetic flowmeters provide fast and accurate flow measurements in applications where other flow techniques, which introduce a flow measurement element (such as an orifice plate) into the process flow, are not suitable. One of the significant costs in the manufacture of the magnetic flowmeter is the flow body through which the process fluid flows. This flow body must bear the process fluid pressure and must not introduce leaks into the process. Typically, the flow body is formed as a tube and includes a pair of flanges that bolt to pipe flanges to create a robust process fluid connection. In order to provide flow body assemblies that are suitable for a variety of different process flow connections, flow bodies are designed and manufactured in order to accommodate different cross-sectional flow areas. However, each cross sectional flow area size, or diameter in the case of a flow tube, offered by the manufacturer typically requires dedicated tooling and manufacturing processes. Thus, additional cost and lead time can be introduced into the manufacturing process due to the availability of such varied flow diameter options.